netdev - [PATCH net-next] net/mlx5e: Ensure macsec_rule is always initiailized in macsec_fs_{r,t}x_add

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Date:   Thu,  8 Sep 2022 08:32:08 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Saeed Mahameed <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, Boris Pismenny <borisp@...dia.com>,
        Raed Salem <raeds@...dia.com>,
        Lior Nahmanson <liorna@...dia.com>, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, patches@...ts.linux.dev,
        Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH net-next] net/mlx5e: Ensure macsec_rule is always initiailized in macsec_fs_{r,t}x_add_rule()

Clang warns:

  drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c:539:6: error: variable 'macsec_rule' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
          if (err)
              ^~~
  drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c:598:9: note: uninitialized use occurs here
          return macsec_rule;
                ^~~~~~~~~~~
  drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c:539:2: note: remove the 'if' if its condition is always false
          if (err)
          ^~~~~~~~
  drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c:523:38: note: initialize the variable 'macsec_rule' to silence this warning
          union mlx5e_macsec_rule *macsec_rule;
                                              ^
                                              = NULL
  drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c:1131:6: error: variable 'macsec_rule' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
          if (err)
              ^~~
  drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c:1215:9: note: uninitialized use occurs here
          return macsec_rule;
                ^~~~~~~~~~~
  drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c:1131:2: note: remove the 'if' if its condition is always false
          if (err)
          ^~~~~~~~
  drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c:1118:38: note: initialize the variable 'macsec_rule' to silence this warning
          union mlx5e_macsec_rule *macsec_rule;
                                              ^
                                              = NULL
  2 errors generated.

If macsec_fs_{r,t}x_ft_get() fail, macsec_rule will be uninitialized.
Use the existing initialization to NULL in the existing error path to
ensure macsec_rule is always initialized.

Fixes: e467b283ffd5 ("net/mlx5e: Add MACsec TX steering rules")
Fixes: 3b20949cb21b ("net/mlx5e: Add MACsec RX steering rules")
Link: https://github.com/ClangBuiltLinux/linux/issues/1706
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---

The other fix I considered was shuffling the two if statements so that
the allocation of macsec_rule came before the call to
macsec_fs_{r,t}x_ft_get() but I was not sure what the implications of
that change were.

Also, I thought netdev was doing testing with clang so that new warnings
do not show up. Did something break or stop working since this is the
second time in two weeks that new warnings have appeared in -next?

 .../net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c    | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c b/drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c
index 608fbbaa5a58..4467e88d7e7f 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec_fs.c
@@ -537,7 +537,7 @@ macsec_fs_tx_add_rule(struct mlx5e_macsec_fs *macsec_fs,
 
 	err = macsec_fs_tx_ft_get(macsec_fs);
 	if (err)
-		goto out_spec;
+		goto out_spec_no_rule;
 
 	macsec_rule = kzalloc(sizeof(*macsec_rule), GFP_KERNEL);
 	if (!macsec_rule) {
@@ -591,6 +591,7 @@ macsec_fs_tx_add_rule(struct mlx5e_macsec_fs *macsec_fs,
 
 err:
 	macsec_fs_tx_del_rule(macsec_fs, tx_rule);
+out_spec_no_rule:
 	macsec_rule = NULL;
 out_spec:
 	kvfree(spec);
@@ -1129,7 +1130,7 @@ macsec_fs_rx_add_rule(struct mlx5e_macsec_fs *macsec_fs,
 
 	err = macsec_fs_rx_ft_get(macsec_fs);
 	if (err)
-		goto out_spec;
+		goto out_spec_no_rule;
 
 	macsec_rule = kzalloc(sizeof(*macsec_rule), GFP_KERNEL);
 	if (!macsec_rule) {
@@ -1209,6 +1210,7 @@ macsec_fs_rx_add_rule(struct mlx5e_macsec_fs *macsec_fs,
 
 err:
 	macsec_fs_rx_del_rule(macsec_fs, rx_rule);
+out_spec_no_rule:
 	macsec_rule = NULL;
 out_spec:
 	kvfree(spec);

base-commit: 75554fe00f941c3c3d9344e88708093a14d2b4b8
-- 
2.37.3